3GPP Long Term Evolution, LTE, is the fourth-generation mobile communication technology standard developed within the 3rd Generation Partnership Project, 3GPP, to improve the Universal Mobile Telecommunication System, UMTS, standard to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, and lowered costs. The Universal Terrestrial Radio Access Network, UTRAN, is the radio access network of a UMTS and Evolved UTRAN, E-UTRAN, is the radio access network of an LTE system. The E-UTRAN consists of base stations called enhanced NodeB (eNB or eNodeB), providing the E-UTRAN user plane and control plane protocol terminations towards the user entities, UE.
Cellular service providers manage their networks for example by splitting cells with multiple base stations or adding additional base stations when the network is heavily loaded. In a heterogeneous network (HetNet) cellular deployment, typically small cells, e.g. picocells, served by pico radio base stations, pRBS, are added in order to off-load the macro cells and to increase coverage. The small cells are especially needed in urban environments, where there are many users and buildings which limit coverage.
For small cell deployments in dense urban environments wireless, Mobile Backhaul, MBH, Non/Near Line-Of-Sight, NLOS, solutions are expected to be predominant. These solutions will be implemented by means of wireless links, connecting the small cell RBS to hubs. In locations where several small cell RBS are needed it is possible that they will be Daisy-chained.
FIG. 1 illustrates the existing technologies. A User Equipment 10, UE, e.g. a mobile/cellular phone, is using a Radio Access Network, RAN, service to access the mobile network services. The radio link 6 is provided by a pRBS. A given pRBS may provide one or a combination of several radio access technologies over the radio link, e.g. 3GPP LTE, 3GPP HSPA, 3GPP GSM or IEEE 802.11x i.e. WiFi. The pRBS needs to backhaul the RAN traffic to the mobile network, and uses an NLOS link 5 for this.
The NLOS link 5 is implemented by means of two terminals on either side of this link, terminal A 1 and B 7. On the Hub side, traffic terminated on terminal B is forwarded to the core network via e.g. a fixed link over copper or fiber media. Terminal A will typically be implemented by using a UE embedded into the pRBS. This UE is referred to as a client. On the Hub side, terminal B will act as an RBS.
Since some of the advantages with LTE are that it offers fast data rate transfer and that it offers fast data transfer in a spectrum-efficient way, including point-to-multipoint connections, it could be desirable to realize the NLOS link 5 with LTE. However, some problems with the existing technology arise when trying to realize the NLOS link with LTE or any other Internet Protocol (IP) based technology; for example, how to establish a backhaul connection and how to find a suitable packet data network gateway, PDN-GW. Hence, there is a need for methods enabling the use of IP based technology in the NLOS link.